Circuit cards, for example, conduction-cooled circuit card assemblies (CCAs) complying with international standards such as IEEE Std. 1101.2-1992, ANSI-VITA 30.1, and ANSI/VITA 48.2, are generally mounted in a card cage or other type of enclosure.
During operation, electronic components on the circuit cards can generate a significant amount of thermal energy that causes the temperature on the circuit cards to increase. This can lead to overheating of critical components on the circuit cards and possible damage to the circuit cards.
Several conventional approaches are available to reduce the temperature inside a card cage. A common approach is to cool a circuit card by conductive cooling, i.e., dissipation or removal of heat from the circuit card to the surrounding card cage via a heat sink, conduction plate, and/or conduction frame attached to the circuit card, which conduct heat from the electronic components on the circuit card to the card cage chassis. This can be achieved by using wedge locks to secure the circuit card to a pair of parallel card guides that extend along an interior sidewall of the card cage to thereby form a thermal joint.
During operation, heat can be transferred away from the circuit card by conduction paths between the circuit card and the card cage chassis. The heat conducting elements in the conduction paths, in particular, the conduction frame and conduction plate of the circuit card, as well as the sidewalls and base of the card cage, are commonly formed of conducting materials such as aluminum, which offer thermal conductivity. However, power consumption levels of components inside the card cage, e.g., circuit cards, backplane, etc., have increased to a point where the thermal requirements of the card cage cannot be satisfied by conventional conduction cooling techniques. In particular, in high-power, conduction-cooled applications, where each circuit card generates a substantial amount of heat, and where card cages are densely packed with heat-generating circuit cards, heat cannot be sufficiently removed from the card cage.